Hydrocarbon conversion process



sept. 23, 1958 v. LIAENSEL- .2,853,437

-HYDROCARBON CONVERSION PROCES Filed May 26. 1955 Rabo m s vl Mw .f TH,M wmf/ W United States Patent tO Y 2,853,437 HYDROCARBON CONVERSIONPROCESS Vladimir Haensel, Hinsdale, lll., assignor to Universal GilProducts Company, Des Plaines, Ill., a corporation of Delaware YApplication May 26, 1955, Serial No. 511,289 6 Claims. (C1. 19e-50) Thisinvention relates to the catalytic conversion of hydrocarbons boilingwithin the gasoline range. Itis more specifically concerned with a novelcombination of catalytic reforming, solvent extraction and fractionationsteps.

The refining industry has been deeply concerned with recent trends inboth the automotive and refining fields which give rise to predictionsof unprecedented increases in gasoline quality in the near future. Inrecognition of these trends, research efforts have been directed towardthe development 'of a practical method. for the produc- I tion of suchsuper quality gasolines.

One process that has recently received commercial attention is thecatalytic reforming process. The term reforming is well known in thepetroleum industry and refers to the treatment of ygasoline fractions toimprove the anti-knock characteristics thereof. A highly successful andeco-nomical reforming process that has achieved wide commercialacceptance is described in my U. S. Patent No. 2,479,110. However, thepresent reforming processes are `all limited by decreasing yields atincreasing octane numbers. There are also other limitations. Forexample, when a full boiling range straight-run gasoline or a relativelywide boiling range naphtha is reformed in the presence of `a catalystthat promotes dehydrogenation of naphthenes and hydrocraclcing ofparafiins, relatively poor yields and considerable fouling of thecatalyst are obtained when the operating conditionsare selected toobtain large octane number appreciation. This apparently is due to thefact that the relatively severe operating conditions that must bemaintained in order to satisfactorily upgrade the higher boilingparaffinic constituents of the feed are too severe for some of the otherconstituents. The result is that an appreciable part of the feed stockis undesirably converted to ygases and to catalyst carbon. Therefore,under the usual conditions of operation the yield of liquid product `andcatalyst life are limited to a considerable extent by and primarilydependent on the decomposition and carbon-forming tendencies of the`higher boiling paraffinic constituents and the aromatic constituents.The higher boiling paratiinic constituents may decompose to form coke onthe catalyst and the aromatic constituents also deposit coke orcarbonaceous material on the catalyst by reacting with each other andforming polynuclear aromatics which are the carbonaceous materials thatfoul the catalyst. I have invented `a method of reforming which largelyovercomes these objectionable features of the prior art reformingprocesses.

It is an object of the present invention to increase the octane lnumberof low octane number ga-solines and fractions thereof.

-It is another object of the present invention to treat low octanenumber gasoline in a system utilizing catalytic reforming, solventextraction, and fractionation so as to obtain a high octane numbergasoline and high yields of liquid product.

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'predominantly .paraflinic fraction into a low boiling Spredominantlyparaini'c fraction land said high boiling predominantly parafinicfraction, and '(-b) Phydrogenand a second hydrocarbon charge containinga high boiling straight-run naphthasfraction and `said low boilingkpredominantly ',parafiinic fra'ctio'n. Y

yIn another embodiment the Ipresent invention relates to a process whichcomprises fractionating a straight-run gasoline fraction 'into at leastalow 'boiling fraction and a high boiling fraction, 'contacting inacatalytic reforming zone hydrogen, said low boiling fraction, and a highboiling Apredominantly parainic'fraction obtained ashereinaf-termentioned,.subjecting the effluentfroms'aid catalytic reforming Zone toasep'aration step to separate lsaid effluent into a predominantlyparafiinic fraction and apredominantly aromatic fraction, fractionatingsaid predominantly parafinic vfractionfinto at .least allow boilingpredominantly parainic fractionland a 'high boiling .predominantly'parafiinic fraction and introducing said high reforming zone, ashereinbefore .mentioned, and there- -aftercontacting in `said catalytic`reforming zon-e hydrogen,

said high boiling fraction, and said low boiling predominantly parafinicfraction.

ln a more specific embodiment my invention relates to a process whichcomprises ifractionating a `straight-run naphtha into a ylow 4`boilingfraction -havingiy an initial boiling point of about 200 F. and an endboiling `point of -about `300 F. and a high boiling fractionv having aninitial boiling point of labout 300 F. `and an end boiling point ofabout 400 F., 'subjecting hydrogen, said low boiling fraction and ahighboiling predominantly parafyfinic fraction obtained as hereinaftersetforth, to contact 'with a catalyst comprising platinum, alumina, andcombined halogen rat reforming conditions, introducing the effluent fromthe catalyticreforming'zone to anextraction zone wherein said effluentis treated with a selective solvent having a relatively Vhigh-er solventpower for aromatics, separately `withdrawing from said extractionizone apredominantly aromatic vfraction and a predominantly parafiinicraiinate, 'fractionating said raffinate into a low boiling predominantlyp'araffinic fraction and a high boiling predominantly paraffinicfraction, introducing 'said high boiling predominantly paraffinicfraction 'to said catalytic reforming zone, and subsequentlyseparately'coutacting said high Vboiling fraction `having yan initialyboiling point of about 300 F. and an end pointof vabout 400 F. and saidlow boiling predominantly parainic fraction to contact with a catalystcomprising platin-um, alumina-and combined halogen in a reforming zoneat reforming conditions.

Briefly, the Ypresent invention provides a method `for effecting animproved yield of 1high octane gasoline from a hydrocarbon chargeboiling in the-gasoline range, and hereinafter referred toas 'theprimary charge, which comprises fractionating the hydrocarbon chargeinto at least two fractions; that is, a low boiling fraction and a highboiling fraction. The low boiling fraction of the primary charge is'combined with a high boiling fraction of apredominantly paraflinicraflinate`,;prepared as lnreinafter set forth, andthe combined stream issubjected .to

reforming in the presence of hydrogen and a suitable reforming catalyst.The heavy fraction, prepared in the prior fractionation of the primarycharge, is combined with a low boiling fraction of a predominantlyparafnic rafhnate, as hereinafter set forth, and this combined streamisV also subjected to reforming in the presence of hydrogen and a`suitable reforming catalyst. For economic reasons it is preferred touse only one reforming zone and to alternately and separately chargeeach of the combined streams as hereinbefore mentioned. For example, thelow boiling portion of the primary charge and the high boiling portionof the predominantly parafinic raii'inate in combination are subjectedto reforming. Subsequently the processing of this combined stream isdiscontinued and the high boiling portion of the primary charge and thelow boiling portion of the predominantly parainic ranate in admixtureare passed to the reforming zone. The invention, therefore, provides fora blocked-out type of operation, that is an operation in which a chargestream is reformed for a period of time, the reforming of thisl chargestream discontinued, followed by the reforming of another charge stream.

In the reforming zone naphthenes are dehydrogenated to aromatics andheavy paraiins are hydrocracked to lower boiling paraifins. It is alsopreferred that the conditions and the catalyst in the reforming zone besuch that there is paran isomerization and paraffin dehydrocyclization.The resulting reformed stream is cooled and the separation thereofeected to provide a gaseous hydrogen-containing stream and anaromatic-rich hydrocarbon stream. The aromatic-rich hydrocarbon streamis fractionated to reject the normally gaseous hydrocarbons produced inthe process and the resultant liquid is passed to a separation zone inwhich the recovery of aromatic hydrocarbons is effected. The resultingnonaromatic or paranic hydrocarbon stream is passed to a fractionationzone wherein the ranate or paraflnic hydrocarbon stream is fractionatedinto at least a low boiling fraction and a high boiling fraction. Eachof these fractions contains predominantly paraflinic hydrocarbons. Thelow boiling fraction is passed to combine with the high boiling fractionprepared by fractionating the primary charge stock. The high boilingpredominantly parainic fraction is passed to combine with the lowboiling fraction of the primary charge stock. As hereinbefore mentioned,each of these combined streams' is separately reformed. Preferably thesame reforming zone is utilized in a blocked-out, or alternate type ofoperation.

A feature of my invention is that greater utilization of the catalystsurface may be achieved by employing the steps of my invention. Ashereinbefore mentioned, the preferred catalyst in the reforming zoneeffects dehydrogenation of naphthenes to form aromatics, thehydrocracking of high boiling parailns to form lower boiling parans, theisomerization of straight chain or slightly branched chain paraflins tomore highly branched chain paraflins, and the dehydrocyclization ofparans to form aromatics. Some of the higher boiling components of thecharge stock, therefore, are hydrocracked on the catalyst surface toform lower boiling parains. Now if the high boiling portion of theprimary charge is reformed in admixture with the high boiling portion ofthe predominantly parainic rafiinate there exists competition for thecatalyst surface; that is, both the heavy naphthenes and the` heavyparains of the charge and the heavy parans of the predominantlyparaffinic rafiinate are competing for the catalyst surface. Similarly,the low boiling hydrocarbons of the charge are preferably improved inoctane number by isomerization and/or dehydrocyclzation. When these lowboiling hydrocarbons of the primary charge are reformed in admixturewith the low boiling components of the predominantly paranic ranate,there again exists a competing of the hydrocarbons for lthe catalystsurface; that is, some of the lower boiling naphthenic hydrocarbons fromthe primary charge stock competes With the lower boiling hydrocarbonsfrom the predominantly parafinic raiiinate. Each of these componentsmust be reacted to achieve an increase in octane number, however, theamount of catalyst surface available is limited and, therefore, thesehydrocarbons' compete with each other for the available catalystsurface. Generally the competing of the hydrocarbons for the catalystresults in lower reforming eiciencies and accordingly lower yields andlower octane numbers. Accordingly when a charge stock is passed over thecatalyst, there is a competition for the available catalyst surface and,therefore, for the reaction among the various species of hydrocarbonspresent. It is indicated that the most strongly adsorbed materials arethe highest boiling aromatic hydrocarbons, while the least stronglyadsorbed materials are the lowest boiling parains. The competition forthe surface is not only on the basis of polarity of the molecule, butalso on the basis of molecular weight, so that in any one particularspecies or type of hydrocarbon, the higher boiling materials areconsiderably more strongly adsorbed on the catalyst surface than thelower boiling member of the species. Thus, high boiling parains areconverted only with diiculty in the presence of high boiling aromatics,while they are converted much more readily in the presence of lowboiling aromatics. In the process of my invention, however, thedisadvantages hereinbefore mentioned are limited by a novel combinationof fractionation. The low boiling fraction of the charge stock is notreformed in the presence of the low boiling fraction of thepredominantly parainic ranate and, therefore, the competing reactionsare not present. The low boiling fraction of the primary charge and thehigh boiling fraction of the predominantly paranic rainate are reformedin admixture. Since the constituents of each of these fractions are in adifferent boiling range and since, generally, each of these fractions isbest reformed by dierent reforming reactions, more eiicient use is madeof the available catalyst surface and higher yields and higher octanenumbers are achieved in the process.

The primary charge stocks which may be reformed in accordance with myprocess comprise hydrocarbon fractions that boil within the gasolinerange and that contain naphthenes and paraflins. The preferred stocksare those consisting essentially of naphthenes and parans, althougharomatics and minor amounts of oleiins may be present. This preferredclass includes straight-run gasoline, natural gasoline and the like. Thegasoline fraction may be a full boiling range gasoline having an initialboiling point within the range of from about 50 F. to about 100 F. andan end boiling point within the range of from about 350 F. to about 425F. or it may be a selected fraction thereof which usually is a higherboiling fraction commonly referred to as naphtha and having an initialboiling point within the range of from about 150 F. to about 250 F. andan end boiling point within the range of from about 350 F. to about 425F. Mixtures of the various gasolines and/ or gasoline fractions may alsobe used and thermally cracked and/or catalytically cracked gasolines maybe used as charging stock. However, when these unsaturated gasolinefractions are used, it is preferred that they be used either inadmixture with a straight-run or natural gasoline fraction, or elsehydrogenated prior to use.

In accordance with the present invention, a charge stream, comprising afraction of the primary charge and a fraction of a rainate recycle, issubjected to a reforming operation in a reforming zone maintained atreforming conditions. In accordance with the invention the charge to thereforming zone may be a mixture of a low boiling portion of the primarycharge and a high boiling portion of the predominantly parainic ranate,or the charge may be a high boiling portion of the primary charge and alow boiling fraction of the predominantly parainic ranate. The lowboiling fraction of the primary charge preferably has an initial boilingpoint within the range of from about 150 F. to about 250 F. and an endpoint within the range of from about 275 F. to about 325 F. The lowboiling fraction of the predominantly parainic fraction or'rafnate alsopreferably has initial and end boiling points within the respectiveranges. The high boiling fraction of the primary charge and the highboiling fraction of the predominantly parafnic fraction or raflnatepreferably has an initial boiling point within the range of from about250 F. to about 320 F. and an end boiling point within the range offromV about 330 F. to about 425 F. These charge streams are separatelyreformed and when the same reforming zone is utilized the charge streamsare separately reformed in a blocked-out type of operation. Either ofthe charge streams may be reformed first followed by the reforming ofthe other charge stream. For a better understanding of the invention theoriginal charge stock, that is the charge stock to the firstfractionator is referred to as the primary charge. The reforming reactorcharge will, therefore, be either a low boiling fraction of the primarycharge and a high boiling fraction of the rafnate, or a high boilingfraction of the primary charge and a low boiling fraction of theraffinate.

Various types of desirable and suitable catalysts may be used in thereforming zone of the process, however, the preferred operation utilizesa supported platinum catalyst in the reforming zone. The catalyst thatmay be used in the reforming zone of my invention comprises thosereforming catalysts that permit dehydrogenation of naphthenichydrocarbons, hydrocracking of paraflinic hydrocarbons, isomerization ofparaflinic hydrocarbons, and dehydrocyclization of paraflinichydrocarbons. A satisfactory catalyst comprises aplatinum-alumina-silica catalyst of the type described in U. S. PatentNo. 2,478,916, issued August 16, 1949. A preferred catalyst comprises aplatinum-alumina-combined halogen catalyst of the type described in myU. S. Patent No. 2,479,109, issued August 16, 1949. Other catalysts suchas molybdenaalumina, chromia-alumina, and platinum on a support, such asa cracking catalyst base may be used. The platinum concentration in thepreferred catalyst may range up to about by weight of the alumina, but adesirable catalyst may be provided to contain as low as from about 0.01%to about 1% by weight of platinum. The halogen ions may be present in anamount of from about 0.1% to about 8% by weight of the catalysts butpreferably are present in an amount of from about 0.1% to about 3% byweight of the nal catalyst on a dry basis. Also, while any of thehalogen ions provide a desirable catalyst the fluoride ions areparticularly preferred and next in order are the chloride ions, thebromide ions, and iodide ions.

The conditions in the reforming zone should be such that substantialconversion of naphthenes to aromatics, relatively mild hydrocracking ofparains, isomerization of paratns, and dehydrocyclization of paraifinsare induced. Usually the conditions in the reforming zone are, atemperature within the range of from about 600 F. to about 1000 F., apressure of from about 50 to about 1000 pounds per square inch, and aweight hourly space velocity of from about 0.5 to about 20. The weighthourly space velocity is defined as the weight of oil per hour perweight of catalyst in the reaction zone. It is preferred that thereforming reactions be conducted' in the presence of hydrogen. In oneembodiment of the process sufficient hydrogen will be produced in thereaction to furnish the hydrogen required in the process and, therefore,it may be unnecessary to introduce hydrogen from an external source orto recycle hydrogen within the process. However, it may be preferred tointroduce hydrogen from an external source generally at the beginning ofthe operation and to recycle hydrogen within the process in order to beassured of a sufficient hydrogen atmosphere in the reaction zone. Thehydrogen present in the reaction zone may be within the range of fromabout 0.5 to about 20 mols of hydrogen per mol of hydrocarbon. In somecases the gas to be recycled will contain hydrogen sulde introduced withthe charge or` liberated by the catalyst and it is within the scope ofthe present invention to treat the hydrogen-containing gas to removehydrogen sulfide or other impurities before recycling the hydrogen tothe reforming zone. At these conditions there are substantially noolefms present in the effluent stream from the reaction Zone.

The effluent from the reforming zone is usually passed through a coolerand into a separator. In the separator a separation is effected toprovide a gaseous hydrogencontaining stream and an aromatic-richhydrocarbon stream. 'At least a portion of the hydrogen-rich gas streamis recycled to the reforming reactor. The aromatic-rich hydrocarbonstream is usually passed to a stabilizer which effects the separation ofthe normally gaseous material which comprises hydrogen, hydrogensulfide, ammonia, and hydrocarbons containing from one to four carbonatoms per molecule, from the normally liquid hydrocarbons. A moreconcentrated aromatic fraction is then obtained in accordance with thepresent invention by subjecting the reformate, containing aromatichydrocarbons to a separation process subsequent to being -suitablytreated to improve its characteristics as a charge stock for theseparation process.

Any suitable separation process may be used to separate the reformateinto a predominantly para'inic fraction and a predominantly aromaticfraction. Suitable processes are solvent extraction, solid absorption,fractional crystallization, etc. Of these the solvent extraction processis preferred since it appears to form a predominantly parainic fractionthat is most suitable for recycling to the reaction zone. v

Solvent extraction processes are used t-o separate certain components ina mixture from other components thereof `by a separation process basedupon a difference in solubility of the components in a particularsolvent. It is frequently desirable to separate various substances bysolvent extraction when the substances to be separated have similarboiling points, are unstable at temperatures at which fractionation iseffected, form constant boiling mixtures, etc. It is particularlydesirable to separate aromatic hydrocarbons from a petroleum fractioncontaining these aromatic hydrocarbons by solvent extraction because apetroleum fraction is normally a continuous mixture of hydrocarbonswhose boiling points are extremely close together and because thepetroleum fraction contains numerous cyclic compounds which tend to formconstant boiling or azeotropic mixtures. As hereinoefore stated, theybasis of a solvent extraction separation is the diiference insolubility in a given solvent of one `of the substances to be separatedfrom the other. It may, therefore, be -seen that the more extreme thisdifference, the easier the separation will be, and an easier separationreects itself process-wise, in less expensive equipment and greateryields per pass in the use of processing equipment as well as in higherpurity of product.

A particularly preferred solvent for separating aromatic hydrocarbonsfrom non-aromatic hydrocarbons is a mixtue of water and a hydrophilicorganic solvent. Such a solvent may have its solubility regulated byadding more or less water. Thus, by adding more water to the solvent,the solubility of all components in the hydrocarbon mixture are reduced,but the solubility difference between the components is increased. Thiseffect is reected process-wise in less contacting stages required toobtain a given purity of product, however, a greater 7 throughput `ofsolvent must be used in order to obtain the same amount of materialdissolved.

As hereinbefore stated, the solvent to be used in this invention ispreferably a mixture of a hydrophilic organic solvent and water, whereinthe amount of water contained in the mixture is selected to regulate thesolubility in the solvent of the materials to be separated. Suitablehydrophilic organic solvents include alcohol, glycols, aldehydes,glycerine, phenol, etc. Particularly preferred solvents are diethyleneglycol, triethylene glycol, dipropylene glycol, tripropylene glycol, andmixtures thereof containing from about 2% to about 30% by weight ofwater.

In classifying hydrocarbon and hydrocarbon type cornpounds according toincreasing solubility in such a solvent, it is found that the solubilityof the various classes increases in the following manner: the leastsoluble are the paratins followed in increasing order of solubility bynaphthenes, oleins, diolelins, acetylenes, sulfur, nitrogen, andoxygen-containing compounds and aromatic hydrocarbons. It may thus beseen that a charge stock which is rich in unsaturated compounds willpresent a greater problem in solvent extraction than a .saturated chargestock since the unsaturated compounds fall between the parai'lins andaromaties in solubility. It may be seen that an ideal charge to solventextraction is one containing paraflinic and aromatic hydrocarbonsexclusively.

The paralhnic compounds also differ in their relative solubility in thesolvent. The solubility appears to be a function of the boiling point ofthe parah'in, with the lower boiling or lighter parains being moresoluble than the higher boiling or heavier parains. Therefore, whenheavy paraliins are dissolved in the solvent, they may be displaced fromthe solvent by adding lighter paratlins thereto. In an embodiment ofthis invention it is preferred to recycle the heavier paramns to thereforming zone and therefore a light paraflin is charged to theextraction zone to displace these heavier parains from the solvent byputting the heavier paraiiins into the rafiinate phase.

In accordance with the present invention the raffinate, which comprisespredominantly paraflinic hydrocarbons, is passed to a fractionation zonewherein the raiiinate is fractionated into at least two fractions, a lowboiling fraction and a high boiling fraction. The low boiling fractionof the ratiinate is combined with the high boiling fraction of theprimary charge stock as hereinbefore specified and the high boilingfraction of the raffinate is combined with the low boiling fraction `ofthe primary charge stock as hereinbefore specified. Each of thesecombined streams is separately reformed in accordance with the presentinvention.

Additional features and advantages of my invention will be apparent fromthe following description of the accompanying drawing which illustratesa particular method for conducting a gasoline upgrading operation inaccordance with the present invention.

Referring nowto the drawing, a straight-run gasoline fraction having aninitial boiling point of 200 F. and an end boiling point of 400 F. ispassed through line 1, is picked up by pump 2, and discharged throughline 3 containing valve 4 intovfractionator 5. A low boilingfraction'having an end point of about 300 F. is removed overhead fromfractionator 5 through line 6, passes through cooler 7, line 8, and intoreceiver 9. A portion of the light or low boiling fraction in receiver 9may be removed through line 12. Another portion is removed from receiver9 through line 10 and passes through line 11 into an upper portion offractionator 5 as retiux. Another portion of the low boiling fractionhaving an initial boiling point of V200 F. and an end point of 300 F. isremoved through line lt) `and passes through lines 13 and 13 intostorage tank 14. A high boiling portion of a rainate, prepared ashereinafter specified, also enters storage tank 14 through lines 77 and13. A heavy or high boiling fraction having a boiling range of fromabout 300 F. to Vabout 400 F. is withdrawn from fractionator 5 throughline l5 and passes through lines l and 18' into storage tank 19. A lowboiling fraction of a ratiinate, prepared `as hereinafter specified, isalso passed into storage tank 19 through lines 71 and 13'. Heat isprovided for the fractionation in fractionator 5 by reboiler 16 withconnecting lines l5 and 17.

ln the operation illustrated in the drawing, a single reaction zone Z7is utilized; however, two or more in series or parallel may be used. Thecharge materials in storage tanks 14 and 19 are separately passedthrough reactor 27. ln the operation herein illustrated valve 26 may beassumed to be closed and valve 2h opened. The charge material in storagetank 14 is withdrawn through line 2l containing open valve 20 and mixeswith hydrogen recycle in line 22 and the combined stream in line 23passes into heater 24 wherein the combined stream is heated to atemperature of 900 F. The heated combined stream is withdrawn fromheater 24 by way of line E5 vand passes into reforming reactor 27.

AReforming reactor 27 contains a bed of spherical catalyst ofapproximately 1A; inch diameter containing 0.4% platinum, 0.1% combinedfluorine, and 0.5% combined chlorine. The pressure in the reactor is 500pounds per square inch, the weight hourly space velocity 4,A and thehydrogen to hydrocarbon mol ratio 5 to l. During the passage of thecharging stock through reactor 27 the buik of the naphthenes containingsix or more carbon atoms per molecule are dehydrogenated to thecorresponding aromatics and a portion of the paraiiins are hydrocrackedto lower boiling parafns. Some isomerization of the paraffins also takesplace. This reaction being of particular importance in the case ofnormal hexane as this hydrocarbon is of relatively low octane number anddoes not readily dehydrocyclicize. The important octane numberVincreasing reaction of dehydrocyclization also occurs in reactor 27. Bythis reaction, a substantial portion of the paraftins are converted intoaromatics.V This reaction is extremely important in increasing theoctane number of the paraffins which are recycled to the reformingreactor through line 77. The conditions in the reforming zone or reactor27 are such that there are substantially no olenic substances produced.

The eliiuent from reactor 27 passes through line 28, cooler 29, line 28and into separator or receiver 30. Hydrogen is withdrawn from the top ofreceiver 36 through line 3l. Makeup hydrogen or hydrogen added to thesystem may be added through line 32 containing valve 33. Excess hydrogenmay also be withdrawn through line 32` At least a portion of thehydrogen in line 31 passes through line 36 and is picked up bycompressor 37 'and discharged into line 22 and combines with the chargein line 2l and the combined stream passes through line 23 into heater24,

The liquid hydrocarbons, comprising the reformate and the bulk of thenormally gaseous hydrocarbons produced in the process, are withdrawnfrom receiver 30 through line 38 and passed into fractionator orstabilizer 40. Normally gaseous hydrocarbons are removed overheadthrough line 41. In stabilizer 4t) the normally gaseous material, whichincludes hydrogen, ammonia, hydrogen sulfide, and hydrocarbon gasescontaining from one to four carbon atoms per molecule, is separated fromthe hydrocarbon liquid comprising aromatic hydrocarbons and parainichydrocarbons.

The gaseous material passes overhead through line 41 into cooler 42,wherein a portion of the material is condensed and the entire streampasses through line 43 into receiver-44. ln receiver 44 the liquid phaseand the gaseous phase of theoverhead material separate. The gaseousphase passesthrough line 46 from which it may be vented to theatmosphere or used as fuel or else it may be further used in the presentprocess or other processes. Thev stabilizer has heat provided thereto byreboiler 48 and connecting lines 47 and d". The conditions in thestabilizer 40 may be such that C4 and lighter components are removed asoverhead, however, the gasolinetherein may be cutdeeper, that is C or C5hydrocarbons may be removed overhead through line 41. However in theusual operation only C., and lighter components are removed as overhead.It is contemplated that the stabilizer and receiver will operate at asufficient pressure to liquefy at least a portion of the overheadmaterial so that a liquid reliux stream may be available to improve theseparation in stabilizer di?. The liquid reflux passes from receiver 44through line 45 into an upper portion of stabilizer 4h.

The stabilizer bottoms which, as hereinbefore stated, comprisesubstantially parafnic and aromatic hydrocarbons, are passed throughlines 47 and 50 into a lower portion of extractor 52. In extractor 52the hydrocarbon material rises and is counter-currently contacted at 300F. and 165 pounds per square inch pressure, in the liquid phase with adescending stream of a selective solvent. In this embodiment diethyleneglycol is used, with the latter entering the upper portion of extractor52 through line 53. Water may also be introduced into extractor 52through line 58 containing valve 59 which is shown aS entering the topof extractor 52; however, the water may also be added to line 53. Thewater content of the diethylene glycol and water mixture is maintainedat about 3% in this embodiment. As hereinbefore mentioned, the water isadded to increase the selectivity of the sol vent in line 53. As aresult of the countercurrent contact of the selective solvent andhydrocarbon stock, the aromatic hydrocarbons contained in the chargestock in line 50 are selectively dissolved in the solvent therebyforming an extract stream containing the solvent and the bulk of thearomatic hydrocarbons and a predominantly paraflinic raffinate streamcontaining the bulk of the paraffinic hydrocarbons.

The raffinate stream passes from the upper portion of extractor 52through line 54 while the extract stream passes from the lower portionof extractor 52 through line 56. The liquid in line 56 is introduced tostripper 60 wherein the dissolved aromatic hydrocarbons and Inino1-quantities of dissolved paraflins are separated from the selectivesolvent. The separation in stripper 60 is not diicult in that thearomatic hydrocarbons are substantially different in nature from theselective solvent as well as having a substantially different boilingpoint. The aromatic hydrocarbon stream along with some light parainspasses overhead through line 61 and may be recovered as product orsubjected to a further rectification or purification step. Heat isprovided for the stripping operation by reboiler 63 and connecting lines62 and 64. The solvent stream is taken from the bottom of stripper 60through line 53 and is passed into the upper portion of extractor 52.

The rainate stream from extractor 52 which is withdrawn through line 54is passed into rafnate fractionator 51. The raffinate may containdissolved or entrained solvent and may be subjected to a settling and/orwashing operation to remove the solvent from the hydrocarbons. Theraffinate may contain components lighter than it is desired tocatalytically reform and also the raffinate may contain components thatare heavier than it is desired to reform, and these components may beremoved in fractionator 51. The primary purpose of fractionator 51 is toseparate the raflinate into a low boiling fraction and a high boilingfraction. In the embodiment herein illustrated, material having an endpoint of 200 F. is taken olf overhead through line 66, passes throughcooler 67 and line 68 into overhead receiver 69. A portion of theliquefied material in receiver 69 may be removed through line 70. Aportion of the liquefied material is also returned to an upper portionof fractionator 51 through line 70 as reflux toy aid inthe sepafation of:components in the fractionator 51. In the embodiment illustratedtherefore components boiling below about 200 F. are removed as overhead.Itis generally undesirable to reform components having a boiling pointabove about 400 F. since it has been found that these heavy componentsgenerally tend to deposit coke on the catalyst and thereby deactivatethe catalyst. In the embodiment herein illustrated components boilingabove about 400 F. are removed through lines 74- and 74. Heat isprovided for the'fractionation in fractionator 51 by reboiler 75 andconnecting lines 74 and 76. The withdrawal lines 71 and 77 are locatedon the column and the column operated so that the material withdrawnfrom fractionator 56 through line 71 has a boiling range of about 200F.-300 F. The high boiling fraction removed through line 7'7 has aboiling range of about 300 F.-400 F. A portion of the low boilingraffinate in line 71 may be removed through line 72 containing valve 73and the remaining portion is passed through line 71 and line 18 intostorage tank 19 wherein it is vmixed with the high boiling fraction ofthe primary charge introduced into storage tank 19 through lines 18 and18'.

Similarly a portion of the high boiling fraction of the raffinate inline 7'7 may be withdrawn through line 73 containing valve 79 and theremaining portion in line 77 passes through line 13 into storage tank14. In storage tanke 14 the heavy raflinate fraction introduced throughlines 77 and 13 is mixed with the light fraction of the primary chargeintroduced into storage tank 14 through lines 13 and 13.

After a period of operation in which valve 26 is closed and valve 20open, the operaion is switched to reforming the material in storage tank19 by opening valve 26 and closing valve 20. In this operation thematerial in tank 19 passes through line 26', valve 26, mixes with thehydrogen recycle in line 22 and the combined stream in line 23 passesinto heater 24. After a period of operation on the charge stock instorage tank 19 valve 26 may be again closed and valve 20 opened toreform the charge Y material in storage tank 14.

Although the process illustrated in the drawing represents one of thepreferred forms of my invention, it is to be understood that myinvention is not limited thereby. A number of variations may beintroduced into the process without departing from the scope of saidinvention.

The following examples are given to further illustrate my invention, butare not given for the purpose of unduly limiting the generally broadscope of said invention.

EXAMPLE I Table Charge Stock Product Percent; Ischexaue, Net PercentMethyl- Mol Percent Benzene, n-Hexano eycloof Total Mol Percent pentaneI-Iexanes From the above table it may be noted that the presence of anaphthene markedly decreased the isomerization of n-hexane. In myinvention after the methylcyclopentane is converted the n-hexane may berecycled to the reaction zone for isomerization.

EXAMPLE II A naphtha fraction having an initial boiling point of 178 F.and an end boiling point of 398 F. is passed through a bed ofplatinum-alumina-combined halogen catalyst comprising alumina containing0.3 by weight of platinum and 0.2% by weight of iiuorine, at a pressureof 700 pounds per square inch, a hydrogen to hydrocarbon mol ratio of 7,a weight hourly space velocity of 4, and an initial average catalysttemperature f 905 F.

The effluent from the reaction zone is cooled and the C4 and lightercomponents removed by fractional distillation. The remaining liquid iscountercurrently contacted in a sieve deck tower With a descendingstream of 96% diethylene glycol and 4% water. The contact is effected at315 F. and approximately 150 pounds per square inch pressure. Theraffinate is removed from the top of the tower and the extract isremoved from the bottom of the tower. The aromatics are recovered fromthe extract by fractional distillation. The raffinate is fractionated toform a low boiling fraction having an initial boiling point of 175 F.and an end boiling point of 300 F. and a high boiling fraction having aninitial boiling point of 300 F. and an end boiling point of 400 F. Thelow boiling fraction is collected in storage tank A and the high boilingfraction of the raiiinate is collected in storage tank B.

After collecting a substantial amount of material in storage tanks A andB the primary charge stock is discontinued from being sent to thereforming reactor and the primary charge stock is now introduced into afractionator. In the fractionator the 178 F.-398 F. primary charge isfractionated into a light fraction having an initial boiling point of178 F. and an end boiling point of 302 F. and a high boiling fractionhaving an initial boiling point of 302 F. and an end boiling point of398 F. The light fraction of the primary charge stock, that is the 178F.-302 F. fraction is passed into storage tank B wherein it is mixedwith ti e 300 F.-400 F. fraction of the predominantly parafiinicraffinate. The 302 F.- 398 F. fraction of the primary charge is passedinto storage tank A wherein it 'is mixed with the 175 F.- 300 F.fraction of the predominantly parainic raffinate.

The mixture in charge tank A is passed through the bed ofplatinum-alumina-silica catalyst at the conditions hereinbeforespecified and the etiluent is solvent extracted with diethylene glycolat the conditions hereinbefore specified and the raffinate obtainedfractionated to provide a 175 F.-300 F. fraction which is recycled tostorage tank A and a 300 F .-400 F. fraction which is passed to chargetank B. After a period of operation on charge tank A, the operation isdiscontinued and the charge material in charge tank B is separatelyreformed. After discontinuing the operation on the charge material incharge tank B the charge tanks may again be switched and the material incharge tank A reformed.

I claim as my invention:

l. A hydrocarbon conversion process which comprises catalyticallyreforming gasoline boiling hydrocarbons in a reforming zone, separatingfrom the eiiuent of the reforming zone a predominantly aromatic fractionand a predominantly parafhnc fraction, fractionating the lastnamedfraction into a light parainic fraction boiling below about 325 F. and aheavier parafnic fraction boiling below about 425 F., separatelyfractionating a straightrun naphtha and separating therefrom a lightnaphtha fraction boiling below about 325 F. and a heavier naphthafraction boiling below about 425 F., commingling said light naphthafraction with said heavier paraffmic fraction and supplying theresultant mixture to said reforming zone,commingling Vsaid heaviernaphtha fraction with said light parailinic fraction and catalyticallyreforming the mixture thus formed independently of the first-mentionedmixture.

2. A hydrocarbon conversion process which comprises reforming gasolineboiling hydrocarbons in contact with a reforming catalyst, separatingfrom the reformed products a predominantly aromatic fraction and apredominantly paranic fraction, fractionating the lastnamed fractioninto a light parainic fraction boiling below about 325 F. and a heavierparafnic fraction boiling below about 425 F., separately fractionating astraightrun naphtha and separating therefrom a light naphtha fractionboiling below about 325 F. and a heavier naphtha fraction boiling belowabout 425 F., commingling said light naphtha fraction Withsaid heavierparaifinic fraction, commingling said heavier naphtha fraction with saidlight parafnic fraction and alternately reforming the resultant mixturesin the presence of said catalyst.

3. A hydrocarbon conversion process which comprises -catalyticallyreforming gasoline boiling hydrocarbons in a reforming zone, separatingfrom the effluent of the reforming zone a predominantly aromaticfraction and a predominantly parainic fraction, fractionating thelastnamed fraction into a low boiling paratinic fraction having aninitial boiling point within the range of from about F. to about 250 F.and an end boiling point within the range of from about 275 F. to about325 F. v

and a high boiling parafnic fraction having an initial boiling pointwithin the range of from about 250 F. to about 320 F. and an end boilingpoint within the range of from about 330 F. to about 425 F., separatelyfractionating a straight-run naphtha and sepa rating therefrom a lowboiling naphtha fraction having an initial boiling point within therange of from about 150 F. to about 250 F. and an end boiling pointwithin the range of from about 275 F. to about 325 F. and 'a highboiling naphtha fraction having an initial boiling point within therange of from about 250 F. to about 320 F. and an end boiling pointwithin the range of from about 330 F. to about 425 F., commingling saidlow boiling naphtha fraction with said high boiling paraffinic fractionand supplying the resultant mixture to said reforming zone, comminglingsaid high boiling naphtha fraction with said low boiling parafiinicfraction and'catalyticallyv reforming the mixture thus formedindependently of the first-mentioned mixture.

4. A hydrocarbon conversion process which comprises reforming gasolineboiling hydrocarbons in a reforming zone in the presence of hydrogen anda platinum-containing catalyst, subjecting resultant reformed productsto solvent extraction to separate therefrom a predominantly aromaticfraction and a predominantly paraflinic raflinate, fractionating saidrainate into a low boiling paranic fraction having an initial boilingpoint within the range of from about 150 F. to about 250 F. and an endboiling point within the range of from about 275 F. to about 325 F. anda high boiling predominantly paranic fraction having an initial boilingpoint within the range of from about 250 F. to about 320 F. and an endboiling point within the range of from about 330 F. to about 425 F.,separately fractionating a straight-run naphtha and separating therefroma low boiling naphtha fraction having an initial boiling point withinthe range of from about 150 F. to about 250 F. and an end boiling pointwithin the range of from about 275 F. to about 325 F. and a high boilingnaphtha fraction having an initial boiling point within the range offrom about 250 F. to about 320 F. and an end boiling point within therange of from about 330 F. to about 425 F., commingling said low boilingnaphtha fraction with said high boiling parafnic fraction and supplyingthe resultant mixture to said reforming zone, commingling said highboiling naphtha fraction with said low boiling paranic fraction andindependently reforming the mixture thus formed in 13 the presence ofhydrogen and a platinum-containing catalyst.

5. The process of claim 3 further characterized in that said mixturesare independently reformed by alternate processing thereof in saidreforming zone.

6. The process of claim 4 further characterized in that said mixturesare independently reformed by alternate processing thereof in saidreforming zone.

References Cited in the le of this patent UNITED STATES PATENTS Burk etal. June 8, 1943 Goldsby Ian. 1, 1946 Tarnpoll Feb; 28, 1956 FOREIGNPATENTS GreatV Britain Dec. 15, 1954

1. A HYDROCARBON CONVERSION PROCESS WHICH COMPRISES CATALYTICALLYREFORMING GASOLINE BOILING HYDROCARBONS IN A REFORMING ZONE, SEPARATINGFROM THE EFFLUENT OF THE REFORMING ZONE A PREDOMINANTLY AROMATICFRACTION AND A PREDOMINANTLY PARAFFINC FRACTION, FRACTIONATING THELASTNAMED FRACTION INTO A LIGHT PARAFFINIC FRACTION BOILING BELOW ABOUT325*F. AND A HEAVIER PARAFFINIC FRACTION BOILING BELOW ABOUT 425*F.,SEPARATELY FRACTIONATING A STRAIGHTRUN NAPHTHA AND SEPARATING THEREFROMA LIGHT NAPHTHA FRACTION BOILING BELOW ABOUT 325*F. AND A HEAVIER NAPTHAFRACTION BOILING BELOW ABOUT 425*F., COMMINGLING SAID LIGHT NAPHTHAFRACTION WITH SAID HEAVIER PARAFFINIC FRACTION AND SUPPLYING THERESULTANT MIXTURE TO SAID REFORMING ZONE, COMMINGLING SAID HEAVIERNAPHTHA FRACTION WITH SAID LIGHT PARAFFINIC FRACTION AND CATALYTICALLYREFORMING THE MIXTURE THUS FORMED INDEPENDENTLY OF THE FIRST-MENTIONEDMIXTURE.